"The sad fact that few conservationists care to face is that many species, perhaps most, do not seem to have any conventional value at all, even hidden conventional value. True, we can not be sure which particular species fall into this category, but it is hard to deny that there must be a great many of them. And unfortunately the species whose members are the fewest in number, the rarest, the most narrowly distributed — in short, the ones most likely to become extinct — are obviously the ones least likely to be missed by the biosphere. Many of these species were never common or ecologically influential; by no stretch of the imagination can we make them out to be vital cogs in the ecological machine. If the California condor disappears forever from the California hills, it will be a tragedy: but don’t expect the chaparral to die, the redwoods to wither, the San Andreas fault to open up, or even the California tourist industry to suffer — they won’t."
from "Why Put a Value on Biodiversity?" by David Ehrenfeld